1. Field of the Invention
This invention relates to a screw with anti-loosening means, which has a securing element with a ring section and thus can be placed around a shaft of the screw under a head of the screw, and when the screw is screwed to a base prevents the screw from being turned back counter to a tightening direction. On the side of the ring section facing an associated surface of the base, the securing element has at least one projection that can be pressed into the surface as the screw is screwed in.
2. Discussion of Related Art
A screw with an anti-loosening means is disclosed in European Patent Reference EP 2 110 567 A2. In one embodiment (FIGS. 27, 28), the anti-loosening means has a ring section under the screw head, with an underside oriented toward a base having sharp projections, which as the screw is tightened, are pressed into the associated surface of the base oriented toward it. In another embodiment (FIGS. 47, 48), the underside of the ring section has tabs that engage in an oblong hole in the base and on its top surface has a cylindrical ring that has tabs punched out from it, which point in the circumferential direction and cooperate with an inhibiting structure of the screw. This design is relatively complex and even when used, unfavorable situations can arise, which result in a disadvantageous operation.
U.S. Pat. No. 3,419,057 A discloses a screw with an anti-loosening means, which has a ring-shaped disk having a tab protruding radially from the side, which engages in a groove, and has a projection, which is oriented axially relative to the screw head and cooperates with an inhibiting structure provided on the circumference of the screw head. Such design does not provide a reliable hold on a base with a flat surface and disadvantages may also arise during operation.
Another screw with an anti-loosening means is disclosed in German Patent Reference DE 10 2006 029 253 B3. The anti-loosening means has a securing element that can be placed under a head of the screw around a threaded shaft, which is embodied in the form of a washer that is bent in an initial state and is of a plastically deformable material. The anti-loosening means secures the screw to prevent it from loosening through reverse rotation.
Other different anti-loosening means for screws, which are based on inhibiting structures that act between the screw head or a nut and a retaining washer or are based on a spring-elastic action are disclosed in German Patent References DE 20 2007 019 121 U1, DE 20 2009 011 269 U1, DE 20 2010 009 496 U1, DE 10 2005 054 471 A1, DD 212 561, DE 699 01 105 T2, and DE 10 2008 056 368 A1.
Often, screws are used for fastening to different items or for different specific uses in which a spring action or simple surface structures that engage with each other, such as by means of prongs, are not sufficient to achieve a reliable securing. For example, screws or nuts with such an anti-loosening means can in connection with different surfaces, which in turn are, for example, soft or elastic, come loose in unfavorable circumstances such as cases involving vibrations or jolting.